1. Field of the Invention
The present invention relates generally to a reusable assembly for heating and dispensing of microwaveable hot melt adhesive materials and to a dispensing material charge for use therein.
2. Description of the Related Art
In the use of hot melt adhesives and other flowable materials which are desirably dispensed in heated condition at the locus of application, the packaging of the heatable, flowable (at least in the heated state) material is an aspect of fundamental importance in the deployment of the material.
Many of such materials immediately prior to their dispensing at the application locus are suitably heated by microwave, ultrasonic, infrared, or other thermal radiation means, to provide the material at the appropriate temperature for the dispensing operation, e.g., in a readily flowable or self-leveling state. For such heating, it is preferable to deploy the material in a heatable form, in a package in which it may also be heated as well as subsequently dispensed.
In the provision of such packaging for sequential storage, heating and dispensing of heated materials, a wide variety of packaging designs has been proposed by the prior art for microwave-heated materials, such as hot melt adhesives which are provided in solid stick form and which under microwave irradiation melt to form a flowable hot melt adhesive medium for bonding and sealant applications.
International Patent Application No. PCT/US91/08661 published Jun. 11, 1992 for "Microwave Hot Melt Adhesive Package and Dispenser," describes a package including a flexible pouch defining a chamber containing the hot melt adhesive, with a dispensing means provided as part of the pouch to permit squeezing dispensing of the hot melt adhesive. The package may include an insulating jacket for facilitating the handling of the package, particularly when the adhesive is in the elevated temperature melt form. The insulating jacket may be formed of polypropylene foam or preferably a foam blend of polystyrene and polyphenylene oxide which may be adhered to and laminated with the microwave transparent layer of the container. In the embodiment shown in FIGS. 1-3 of the patent, the insulating jacket comprises an insulating layer which is heat sealed with a microwave transparent layer at edge portions thereof. The hot melt adhesive employed in such package and dispenser is described to be of varying type (e.g., a water-retaining type which does not require microwave susceptors, or alternatively a type including microwave susceptors in the form of microwave susceptor particles blended or mixed in the hot melt adhesive medium).
International Patent Application No. PCT/US92/05604 published Jan. 21, 1993 discloses a microwave activatable adhesive article including the hot-melt or heat-curable adhesive, and a microwave susceptor layer of at least electrically semi-conductive microwave radiation absorbing material. The susceptor layer is disposed on at least a portion of the substrate, and is responsive to exposure to microwave radiation for raising the temperature of the substrate above a desired level sufficient to melt the substrate.
U.S. Pat. 5,188,256 issued Feb. 23, 1993 to J. R. Nottingham, et al. discloses a hot melt adhesive dispenser including a container having hot melt adhesive therein, and a susceptor comprising metal particles adhered to a film such as a high temperature polyimid film, wherein the susceptor is in heat transfer relationship with the hot melt adhesive. The hot melt adhesive container may be formed of a flexible film material having high temperature resistance, and the susceptor may be provided on an interior surface of the container, or otherwise in heat transfer relationship to the hot melt adhesive material. The dispenser disclosed in this patent may further comprise a cover of relatively rigid, heat insulating composite material, such as a foam polystyrene laminated with a bleached hardwood craft paper.
Other hot melt adhesive dispensers are disclosed in co-pending U.S. patent application Nos. 08/020,511, now abandoned; 08/020,622, now abandoned; and: 08/200,852, now U.S. Pat. No. 5,368,199, which variously disclose dispensers in which microwave susceptors are a component of the container for the hot melt adhesive. U.S. application No. 08/200,852 discloses the concept of a reusable package or sleeve accommodating receipt therein of a hot melt adhesive container including as a component of the container a microwave susceptor material.
It is an object of the present invention to provide an improved, and reusable, microwaveable adhesive dispensing assembly, and an adhesive charge adapted for use therewith.
Another object of the present invention is to provide an adhesive charge which is of a readily mass-produceable and low-cost character.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.